Field of the Invention
The present invention relates to an etchant for copper, a replenishment solution therefor, and a method for forming copper wiring.
Description of the Related Art
When a photoetching method is used to form a copper wiring pattern in the production of a printed wiring board, for example, an iron chloride-based etchant, a copper chloride-based etchant or an alkaline etchant is used as an etchant. The use of these etchants may cause copper below the etching resist to be dissolved from side surfaces of the wiring pattern, this phenomenon being called side etching. In other words, there is caused a phenomenon that a portion of copper which is covered with the etching resist to be desired not to be primarily removed by the etching (i.e., a copper wiring portion) is removed by the etchant, so that the copper wiring is made narrower from the bottom of the copper wiring toward the top thereof. In particular, when the copper wiring pattern is fine, it is essential to decrease such side etching as much as possible. In order to restrain this side etching, Patent Document 1 suggests an etchant into which an azole compound that is a five-membered heteroaromatic compound is incorporated.
The etchant described in Patent Document 1 makes it possible to restrain side etching. However, the use of the etchant described in Patent Document 1 in a usual way may unfavorably cause side surfaces of copper wiring to be uneven. When a side surface of the copper wiring is uneven, the copper wiring is lowered in linearity (wiring width (W2) of the top of the copper wiring) (see FIG. 1). Consequently, when the copper wiring width is optically examined from above the printed wiring board, misrecognition may be unfavorably caused. Moreover, when the linearity is extremely deteriorated, the printed wiring board may be lowered in impedance characteristic. Thus, Patent Document 2 suggests an etchant including a specific aliphatic heterocyclic compound and not to cause lowering in the linearity of copper wiring easily.
Patent Document 3 discloses a composition which is used for micro-etching for promoting the adhesion of an imaging resist or a solder mask onto a surface of copper or a copper alloy, and which includes a halide ion source, such as a bromide ion. However, this composition is not an etchant used to form copper wiring.